Light for the elderly

Light is not just for seeing. It sets our inner clock, which governs the running of the whole body, our behaviour and the running of society. How does the lack of light affect people? How can we make up for the lack of light?

It has been known for almost 50 years that our central brain clock resides in the middle of the head, above the optic nerve junction. It sends information about the time of day throughout the body. Each cell knows what time it is and what it should be doing at that time. The daily schedule governs, for example, the secretion of sleep hormone, stress and sex hormones, insulin, body temperature, blood pressure, as well as behaviour, alertness and sleep. This is scientifically called the circadian rhythm (see Figure 1).

We have only known for less than 20 years about another photoreceptor on the retina: the light-sensitive ganglion cells, which are not used for vision but send information to the central clock about the intensity of light in our environment. The circadian rhythm is literally written in our genes, but its "day" is slightly longer than 24 hours. To keep the variations from accumulating, we need a certain amount of relatively bright light each morning to synchronize our biological rhythm with the rotation of the Earth.

How intense does the light need to be, what are its properties, when and how long an exposure is needed to keep us in rhythm, and how does all this relate to age?

How much light?

In short, it can be said that outdoor sunlight is usually sufficient for synchronisation and artificial lighting in buildings alone is usually not sufficient for synchronisation. For reference, the illuminance is given in lux (lx). On a clear summer noon, we measure about 100,000 lux horizontally outside and about 30,000 lux in winter. At dusk it is only a few lux. By contrast, artificial lighting in corridors and client rooms is usually 100 lux, for reading we need 300 lux and the prescription for offices or examination rooms is 500 lux.

The threshold intensity for synchronisation is approximately 2000 lux for a 65-year-old person. We will discuss later how it increases with age and how much time is needed. There is much more light outside than that minimum for most of the day, even with overcast skies. This is why doctors and chronobiologists alike so much recommend morning walks, when one gets a starter dose of light for free and of the best quality. In most cases, only a few percent of the outdoor daylight penetrates into buildings, which is only sufficient for synchronisation in some cases. East-facing windows are a great advantage. Many health and social care facilities are housed in historic buildings, often still with mature trees in front of the windows, where daylight doesn't get a chance.

Artificial lighting with the necessary intensity is also rare in health care or social services, for example in dentists' offices or operating theatres. However, these places are not visited by clients every day.

Lack of light

Thus, some clients may miss the light synchronization cue. The circadian rhythm then runs its own pace, independent of "civil" time, or goes into a chaotic pattern. The benefits of synchronization are there. The individual day no longer lasts 24 hours: periods when the client sleeps at night alternate with periods when he sleeps during the day and then needs increased staff attention at night. Other times, clients sleep steadily during the day and then cannot fall asleep at night. Hypnotics often add to this downward spiral.

Stress caused by prolonged disruption of sleep rhythms is debilitating and can complicate a variety of diseases including diabetes, cancer, cardiac or psychiatric illnesses. It also increases the likelihood of accidents and reduces the client's overall quality of life.

How to fill in the missing light?

If the client is unable to get at least 20 minutes of daylight each morning (limited mobility, closed wards, historical buildings, winter season...), the light can be supplemented with special phototherapy lamps, the application of which should be decided by the doctor. Chronobiological phototherapy (ChBFT) has been used for years in psychiatry to treat depression. Since 2015, it has been reimbursed by health insurance companies (in the Czech Republic for hospitalization in a specialized clinic, in Slovakia reimbursement for outpatient or home treatment is being prepared). The most commonly used therapeutic intensity is 10 thousand lux.

In the social sphere, chronobiological lighting (ChBO) can also be used, which works at a lower intensity and is therefore not therapy in the medical sense.

Best practices

Portable phototherapy luminaire (solar simulator). It is usually a box about 30 × 60 cm. The client sits or lies on his/her side on the bed to which the luminaire is attached. These luminaires are available in table-standing and stand-on-wheel versions. The specified distance must be maintained during application. Typical application is 30 minutes in the morning. It is sufficient for the client to have the luminaire in his field of vision, he does not have to look directly into the light, he can read or have breakfast, for example. One luminaire can be used for several clients in succession. This type of luminaire is inexpensive to purchase and operate, but it does restrict the client's movement to a large extent during the application. It is a good choice for facilities that are beginning to provide chronobiological phototherapy.

Ceiling phototherapy or chronobiological luminaires. Common rooms, dining rooms, playrooms, art therapy rooms or separate phototherapy rooms can be equipped with additional ceiling lights. The application is then usually carried out in groups of clients and over a longer period of time during several morning and mid-morning hours. The illumination at eye level is usually 1000-2000 lx (ChBO) or higher (ChBFT). Higher intensity allows shorter application times. Purchase and operating costs are balanced by the fact that these luminaires allow simultaneous application with multiple clients that do not restrict movement. Sometimes the advantage is that clients cannot reach the luminaires.

Mobile programmable phototherapy luminaire. This type of luminaire is used with clients who spend most of their time in bed. The luminaire is at a height that does not restrict the client's movement or interfere with normal operation. If necessary, it can be easily transported to another bed. The light mode is fully automatic, the luminaire contains a precise clock and the intensity of the light is controlled by a program uploaded to a memory card by the doctor. In addition to morning phototherapy, an all-day increased light regime, biodynamic simulation of sunrise and sunset or low night lighting for delirium clients can be programmed.

Other ways of supplementing light are light glasses, light caps, light tables or rechargeable travel light boxes. However, lower intensity models are only effective up to a certain age.

Properties of therapeutic light

The light-sensitive ganglion cells are most sensitive to the blue light that illuminates the blue sky. Therefore, light of a cool tone with a high proportion of this component is used in therapy. Ordinary cool light would be too harsh, which is why since the 1980s phototherapy has used so-called full-spectrum fluorescent lamps (now also LED), which are closer to sunlight and have a pleasant effect.

Correct timing

The greatest effectiveness of phototherapy is in the morning, until about 9 o'clock. In the social sphere, the start of light application is usually adapted to the mode of the facility. In automatic operation, lighting can be timed according to whether the patient is a lark or an owl. Evening phototherapy is sometimes used for sleep consolidation.

Length of exposure

The standard phototherapy is 10 thousand lux for 30 minutes. At lower intensities, a proportionally longer exposure should be chosen. Sometimes all-day phototherapy is also used, e.g. with a break after lunch. However, the intensity must be above the threshold for the client's age.

Influence of age

The lens of the eye transmits less light with increasing age. If 1000 lux is enough to synchronise us at 30, it is twice as much at 65, three times as much at 80 and four times as much at 90. The circadian rhythm becomes more and more fragile as we age.

Regularity

The effect of phototherapy occurs within a few days, but daily application is necessary to maintain it. One day's downtime does not matter.

Benefits of phototherapy

The main benefit for the client is stabilization of the disturbed daily rhythm, improvement of sleep and alleviation of depression. There is also the potential to reduce the burden on night staff. Clients tolerate phototherapy well and often like it.

Contraindications

Contraindications may be serious eye diseases. For clients with bipolar disorder, the use of a mood stabilizer is a prerequisite.

Side effects

Some clients complain of burning or red eyes at the beginning of the therapy, but after a week they usually adapt to the stronger light and the problems disappear.

Antonín Fuksa is an electrical engineer focused on the development of special luminaires, their control methods and lighting design. As a part of his postgraduate studies at the 1st Faculty of Medicine, Charles University in Prague, he is researching phototherapy for the elderly.